A wind turbine, which is a power generation device for converting wind energy into electric energy, allows blades to be rotated by the wind and produces electricity by way of the rotary power of the blades generated by the rotation.
Such a wind turbine is mainly composed of blades, a gearbox and an electric generator.
The blades are parts rotated by wind to convert wind power energy into mechanical energy. The gearbox is a device for rotating the electric generator by transmitting rotary power generated at the blades to a change gear through a central shaft and increasing the number of rotations to a number required by the electric generator. The electric generator is a device for converting the mechanical energy generated at the blades into electric energy.
Conventional wind turbines are classified into a horizontal axis wind turbine in which a central shaft is installed horizontally to the flow direction of fluid on the basis of the direction of the installation of a shaft, and a vertical axis wind turbine in which a central shaft is installed vertically to the flow direction of fluid on the basis of the shaft installation direction.
The horizontal axis wind turbine is operated in a propeller-rotation manner and has relatively high power generation efficiency, but is disadvantageous in that the direction of a rotor must be changed depending on variation in the flow direction of fluid, and a device for changing the angle of blades depending on the flow velocity of fluid is required.
Here, the term “rotor” means a rotating body including a plurality of blades combined with each other around a central shaft.
Further, the horizontal axis wind turbine is configured such that the central shaft of the rotor is located above at least the radius of the rotor. Accordingly, in order to connect the central shaft of the rotor, located at a higher place, to an electric generator, the horizontal axis wind turbine can be driven only when the shaft of the electric generator and the central shaft of the rotor are arranged at almost the same position by installing the electric generator at the same height as that of the central shaft, or when a device for converting horizontal rotary power into vertical rotary power is additionally installed and is connected to the electric generator. However, the former is problematic in that the risk of causing mechanical damage is present due to the strong flow of fluid, and maintenance is not facilitated. Further, the latter is problematic in that, during a process for converting horizontal rotary power into vertical rotary power, energy loss may occur.
Further, recently, a vertical axis wind turbine has been developed and commercialized, but is problematic in that manufacturing costs are high, repelling power resistant to wind power is produced at blades moving in the reverse direction of wind, and thus rotary power obtained from blades moving in the forward direction of wind is canceled and weakened. Further, when a wind turbine is manufactured to have a large size, a load on a rotating part itself (an entire part rotated by fluid) is very large, so that the effectiveness of power generation is low, and the rotating part does not rotate when fluid flows at low velocity.
Meanwhile, a conventional vertical axis wind turbine includes a central shaft located vertically to the flow direction of fluid and configured to transmit electric power to an electric generator, an upper hub arranged on the top of the central shaft and configured such that a plurality of upper spokes is radially coupled to the upper hub, a lower hub arranged on the bottom of the central shaft and configured such that a plurality of lower spokes is radially coupled to the lower hub, and a plurality of blades, the first ends of which are fixed to the upper spokes of the upper hub and the second ends of which are fixed to the lower spokes of the lower hub.
However, the conventional vertical axis wind turbine is disadvantageous in that, when the flow direction of fluid is not uniform and is fluctuating, the efficiency of energy produced in the vertical axis wind turbine decreases. In other words, since the blades are fixed, the blades cannot maintain an optimized pitch angle with respect to the fluctuating flow direction of fluid.